Machine-to-Machine (M2M) communication enables machines to communicate directly with one another and is expanding rapidly because of the potential to generate significant revenue for mobile network operators. In 3rd Generation Partnership Project (3GPP) context, M2M is also referred to as MTC. MTC uses devices that capture certain events such as temperature, gas or water consumption, and then sent the event over a wired or wireless network to an MTC application. For example, smart meters with metering application are expected to be one among the early MTC devices deployed. Many other MTC devices such as e-health monitors, manufacturing management or tracking in security application, are envisioned and are expected to be widely used in the near future.
FIG. 1 shows a schematic view of the bearer path of MTC device in a conventional communication environment. As shown in FIG. 1, an MTC capillary network 110 includes a plurality of MTC devices 101 and typically one MTC gateway device 102. When a serving gateway (SGW) 103 receives packets for an MTC device 101, SGW 103 sends a downlink (DL) data notification to mobility management entity (MME) 104. Upon receiving DL data notification from SGW 103, MME 104 sends a paging signal to an evolved Node B (eNB) or base station (BS) 105, which, in turn, relays the paging signal to MTC device 101. In response, MTC device 101 establishes a data path through BS 105 to SGW 103 for subsequent MTC data communication. In the above scenario, MTC gateway device 102 is not involved in the bearer path establishment.
Among other ongoing research activities and work, the 3GPP established common and specific service requirements including MTC communication scenarios. According to those, MTC devices may communicate directly with one or more MTC servers. In another communication scenario, so-called local-access devices without 3GPP communication capability are located in a MTC capillary network which provides local connectivity between the local-access devices within its coverage and a MTC gateway device. The MTC gateway device is an MTC device which acts as a gateway for local-access devices in a MTC capillary network to communicate through a public land mobile network (PLMN) with one or more MTC servers. In general, MTC devices may be equipped with both 3GPP and non-3GPP communication capabilities.
On the other hand, network assisted device-to-device D2D communication has been proposed as a means of taking advantage of the physical proximity of communicating devices with the aim to improve local services. D2D communication may provide the following advantages: (1) the proximity of user equipments may allow for extremely high bit rates, low delay and low power consumption; (2) the radio resources may be simultaneously used by cellular as well as D2D links, which improves the usage efficiency of radio resources; and (3) only a single link is used in the D2D mode rather than using both an uplink and a downlink resource when communication via the access point in the cellular mode.
FIG. 2 shows a schematic view of a MTC capillary network including MTC devices with both 3GPP capability and other wireless interface and non-3GPP local access devices. As shown in FIG. 2, MTC capillary network includes a plurality of MTC devices 201, at least a MTC gateway device 202 and a plurality of non-3GPP local access devices 203. A D2D connection can be established between two MTC devices 201, two MTC gateway devices 202 or between an MTC device 201 and an MTC gateway device 202.
When a user equipment (UE) A intends to establish a connection to UE B, a network-assisted D2D link establishment technique may initiate a procedure including: checking whether UE A and UE B are candidates for a D2D connection; triggering transmission of beacon signals to determine link quality; and deciding whether D2D is suitable and allocating resources if so.